Adhesive tapes for sealing cartons or carton flaps during manufacture or after the carton is filled are well known in the art. One of the most common constructions is a standard kraft paper tape, which includes a water-soluble or water activated adhesive on one side. Rolls of this tape can be dispensed through machines, which rely on the longitudinal stiffness of the tape to unwind it from the roll and force it through a tape-moisturizing component. This component includes a water reservoir, which moistens the adhesive surface of the tape and readies it for application to the carton. Often, the tape-moisturizing component includes a heating bar, which enhances the activation of the moistened adhesive through the use of heat, and facilitates wet-out of the adhesive.
Various improvements to this type of tape have been developed over the years to meet differing requirements in the manufacture and sealing of cartons. For example, multiple layered tapes using reinforcing fibers generally made of fiberglass and extending longitudinally and/or angularly across this tape to increase its strength are conventionally used for higher closure strength requirements. Although the tape is harder to tear due to the reinforcing fibers, this construction results in the somewhat rough and uneven surface both along the top and bottom of the tape as well as a tape construction that is somewhat thicker than the conventional kraft tape. This uneven surface and thicker tape causes a standard size roll to be of a shorter length for any given diameter compared to conventional tapes.
Plastic films are also known in the art to provide advantages when used in tape construction. Plastic films tend to be much stronger than paper tapes and resist shearing during package shipping as is common with non-reinforced paper tape. However, plastic film tapes have disadvantages as well.
One problem in using plastic film is that a water-soluble or water activatable adhesive does not easily adhere to plastic film. A second disadvantage inherent in plastic film tape is the lack of longitudinal rigidity, thus making plastic film tape difficult to feed through conventional packing machine.
Recognizing this problem in adhering the water-activated adhesive to the plastic film, Williams in U.S. Pat. No. 4,351,877 disclosed a multiple layered laminated tape having an upper strength layer made of a film of prestretched polypropylene, which is laminated to a lower carrier layer of kraft paper. The carrier layer includes a coating of a water-activated adhesive, which is used to apply the tape to a carton. After application, the plastic layer is stripped away from the carton due to the relatively low bond between the plastic film and the paper carrier, so that the package may be easily opened after removal of the plastic film.
Similarly, Bloch U.S. Pat. No. 5,190,798 discloses a paper plastic film fiber glass reinforced sealing tape which includes a paper inner ply whose exposed face is pre-gummed and a synthetic plastic film outer ply which is laminated by a water based adhesive to the inner ply. Sandwiched between the inner and outer plies is a longitudinal array of fiberglass strands, which serve to reinforce the tape. After a corrugated article is sealed by the tape, it is possible to remove the outer ply by stripping it from the tape, again due to the relatively low bond between the plastic film and the inner paper layer.
However, the tape compositions described in Williams and Bloch undermine tamper resistance of the sealed carton by making the plastic film easily removable.
A tape having a reinforcing means and a tamper resisting means that can be applied to a carton using conventional water-activated packing tape dispensing machines is needed.